This invention relates to a sealing element, and particularly to an improved seal positioned at the fill opening of a removable holding tank of a cassette type sanitary system such as described in the above referenced related application.
The above referenced patent application discloses a cassette type sanitary system particularly adapted to be mounted within the interior compartment of a recreational vehicle (RV). Wastes generated during use of the sanitary system are contained within a holding tank which can be conveniently removed from the RV through an exterior access door where it can be transported to a disposal site and emptied.
As described in detail in the above referenced related application, the waste holding tank has a centrally disposed fill opening within its top wall portion which enables the holding tank to accept waste products from an associated appliance such as a toilet. A seal element surrounds the fill opening and has an upper surface which seals against an associated structure of the sanitary system so that when wastes are transported into the holding tank they will not leak outside the tank. In order to prevent leakage from the holding tank when it is removed from the RV and transported to a disposal site, it is necessary to provide a means for securely closing off the fill opening. Accordingly, a moveable valve blade is mounted within the holding tank which is normally positioned to close off the fill opening but may be actuated to uncover the opening to enable filling of the holding tank. The movable valve blade seals against the lower surface of the seal element to prevent the contents of the holding tank from leaking out and further prevents odors from being vented into the RV when the valve is closed. Additional details of the configuration of a cassette type sanitary system and its operation is presented within the above referenced patent application.
This application is particularly directed to an improved seal element for the holding tank fill opening which provides enhanced resistance to leakage of the material within the holding tank when it is being transported to a disposal site. During transporting of the holding tank, the fill opening and valve blade may be immersed in the liquid wastes in the tank and are therefore subjected to hydrostatic pressure which aggravates leakage problems. Briefly, the seal element according to this invention includes a pair of lips adapted to engage the valve blade in its closed position. One of the seal lips is inclined such that fluid pressure within the holding tank acts on the lip to cause it to more tightly seal against the valve surface, thereby providing enhanced protection against leakage.